Manufacture of soap



Feb. 14, 1939.

.1. A. SCHWANTES MANUFACTURE OF SOAP Fild March 7, 1936 a N R M F V Patented Feb. 14,1939

' UNITED STATES PATENT OFFICE Pal-olive- Oity,N.J.,aootpanthnotDehware ApplieaiionIaroh'LlMh-ialloflm zflahna (CI. 81-16) This invention relates to the treatment of soap. It relates more particularly to the refining of that type oi'soap suitable ioruseasa toiletsoap,i.e.. a partially dried hard soap. It includes a new process and apparatus advantageously used in carrying out the new process. t

Toilet soaps as heretofore produced have been characterized by striations or irregularities in texture. The primary object of the present invention isthe production of a hard, partially dried soap free from striations, air pockets and irregularities in texture and the provision of a process and apparatus designed to produce such soap continuously and economically as a plastic, homogeneous, smooth bar adapted for conversion into cakes of finished soap by a simple stamping operation.

Toilet soaps in general are partially dried, hard soaps containing considerably less water than kettle soaps. They are generally produced from kettle soaps by removing a' portion of the water content oi the kettle soaps and subjecting the resulting partially dry soap to a suitable levigating treatment to plasticize and homogenine it.

In ordinary practice, hot kettle soap is cooled on revolving rolls to form a solidified film which is removed by means of doctor knives in the form of ribbons about one-half to one-eighth inch in width and from one to two-hundredths oiian inch thick. These soap ribbons having a water contents of 28 to 30% are dropped onto a screen belt as they are scraped from the cooling rolls and conveyed into a drying room where they are exposed to warm circulating air to reduce their water content to the desired amount, which may vary from to or more, depending upon the use for which the soap is intended. Soaps intended for domestic purposes are generally dried to about 13 to 15% water and soap for export purposesto about 11 to 12%. The hardness of the final soap depends to a large extent upon its water content, soaps with a relatively large water content being softer than those with a smaller water content.

In this drying operation hard particles or specks frequently form in the partially dried soap. These hard particles or specks are minute particles of soap from which a larger proportion of water is removed than is removed from the bulk of the soap. They form partly because the edges of the soap ribbons tend to lose water more rapidly than the center portions of the ribbons and partly .because in handling the ribbons it is virtually impossible to avoid a certain amount of breakage with formation small chips which, because of their large exposed area, dry more rapidly than themainbulkotthesoap. 'lhesehardspecks orparticlesarealsofrequentiycausedbyimproper storage which allows exposure of a pmtionofthesoaptodryair.

These small hard particles of over-dried soap are objectionable in a finished soap as they impart to it a harsh, gritty texture. 'Ihey do not absorb water readily and they are not readily homogeniaed with'the'rest of the soap. They cannot be eliminated by mere attrition nor by levigation.

. It is n, to produce a toilet soap free from such objectionable hard particles, to crush the particles to such a small size that they are not noticeable. To accomplish this, the partially driedsoapispassedthroughmillingrolis.

In this operation the soap is admixed with perfume. coloring matter, etc., and through a series of rolls set with vely decreasing clearances or bites, the last set of rollsgenerally being set to a clearance of some {to 8 orlO thousandths of an inch. The mixing and milling to which the soap is subjected in the milling mils serve not only to crush the hard particles to asize comparable with the last clearance, but also to levigate and homogenize the soap to insure a uniform product. By setting the clearance of the last set of milling rolls to a few thousandths of an inch all of the hard particles or specks in the soap are reduced to such an extent that they do not impart an objecionable, gritty texture to the final soap even though they are not absorbed by the main body of the soap.

The milled soap with admixed perfume, etc., is then compressed and compacted and extruded into a solid continuous bar of soap suitable for stamping into cakes. In this operation; as usually carried out, the milled soap is fed into a continuous screw or worm revolving within a closed cylinder and compressed and forced through a i'oraminous plate which converts the soap into filaments 01' solid soap of much less bulk than the flakes of milled soap. The soap is then plodded, i. e., these filaments oi soap are then fed to another continuous screw or worm, also rotating in a closed cylinder, which compacts the filaments and forces the compacted mass through a nozzle or orifice as a continuous bar.

Generally in this extrusion operation the cylinder surrounding the worm is cooled by means of water to prevent the soap from becoming too hot and to insure its production in the form of a plastic mass of desired consistency. The nozzle, however, is generally heated so that the surface of the extruded bar has a polished, smooth finish.

The toilet soap thus produced is smooth, homogeneous, and of satisfactory quality, but frequently is characterized by striations or irregularities in texture, which are undesirable. These striations are caused by the inclusion of air in the soap. They are particularly noticeable, and hence objectionable, in colored soap, but are present, so far as I am aware, in all milled or similarly treated partially dried soap. The striations are somewhat reduced hy passing the soap through a screen before extrusion but are present to some extent whether the soap is passed through a screen or not.

My invention provides a process in which the desirable features of the ordinary practice are retained and by which a soap having a smooth texture is obtained; but which in addition eliminates the objectionable striations heretofore present in all milled soaps and thus allows the production of homogeneous plastic soap having all of the desirable properties of toilet soap as heretofore produced, but free from striations orirregularities in texture.

In my process the soap is partially dried and milled in the usual manner to convert it into a plastic homogeneous product free from objectionable hard particles. It is then forced through a screen to remove all foreign material and to compact it into the form of relatively dense illaments or threads occupying relatively little space as compared with the flakes or chips resulting from the ,milling operation. This soap in the form of filaments or threads is then passed through an evacuated chamber which removes all of the air from the mass, and is extruded or plodded while still under the vacuum. By passing the soap, after the preliminary compacting and while in the relatively finely divided state attained when it is forced through the screen, through an evacuated chamber and maintaining the vacuum during the plodding operation, all possibility of including air pockets within the finished soap is precluded and a flssureless, striation-free soap is obtained.

The improvement in soap treated by this process is particularly apparent when colored soaps are so produced, as striations or fissures are particularly apparent in such soaps. The striationfree soap so produced is thoroughly levigated and homogenized by the milling operation and is free from objectionable hard particles. It is uniform in texture and, if during the plodding operation the soap is maintained at a proper temperature, has a desirable plasticity. It differs from prior milled soaps only in the fact that it is free from striations and therefore has a more even texture than such soaps have previously had.

The screening operation to which I subject the milled soap serves the dual purpose of removing allforeign materials from the soap and of reducing the bulk of the soap so that the removal of entrapped air is greatly simplified. It also serves to levigate the soap to a certain extent and to compact it and thereby simplify the final plodding or extruding operation. The size of the orifices in the screen is of no particular importance as long as they contribute the desired screening effect. I prefer, however, to use oriflees of a relatively small diameter, e. g., about 12 to 15 thousandths of an inch so that the diaments of soap so produced are relatively small and do not contain entrapped air which might not be removed in the vacuum chamber. Also, by the use of holes or orifices of such a small diameter, effective screening of the soap is insured.

-shcwn at Ho. 7 serves to increase the capacity of the screen, and

In one embodiment of my invention, I force partially dried milled soap with admixed perfume, coloring matter, etc., thoroughly levigated and with all hard particles crushed to such a size as to be unobjectionable, through a foramincus screen directly into an evacuated chamber whence it drops by gravity into the hopper of a plodder or extrusion machine which is included in the evacuated chamber and is compacted and extruded as a continuous bar of striation-frec soap.

The evacuated chamber is conveniently provided by placing a metal. hood over the exit end of the screen and over the hopper of the plodder or extrusion machine and connecting the included space to a suitable vacuum device such as a steam injector or a vacuum pump. The screen and the nozzle of' the plodder are kept continuously full of soap and thus prevent the entrance of air at these points. It is desirable to maintain a relatively high vacuum, e. g., 27 inches of mercury below atmospheric pressure, more or less, in the evacuated chamber.

The invention will be described in greater detail in connection with the accompanying drawing, but it is not limited thereto. In the drawing:

Fig. l is a sectional view in elevation of a machine for plodding milled soap;

Fig. 2 is a view of part of a grinding head adapted to rotate in contact with the screen of the apparatus;

Fig. 3 is a sectional view of the grinding head along the section H of Fig. 2 showing the construction of the knives; and Fig. 4 is a sectional view of part of the fcraminous plate which is used as a screen.

The machine illustrated in Fig. 1 is adapted for the production of a continuous bar of homogencus, striaticn-free, plastic soap from partially dried milled soap in accordance with the present invention. In this machine, milled soap is fed into opening II from a hopper or a chute (not shown) onto worm H which rotates within cylinder II. The worm carries the soap forward and at the same time compacts or compresses it and subjects it to a certain amount of levigation. The soap is thus forced through grinding head II and foraminous plate It and through the holes of the backing plate it into evacuated chamber ll. The grinding head It is directly attached to worm H and rotate with it. It is shown in greater detail in Figs. 2 and 3. The screen M consistsofasheetmetaldischavingamyriadot' small conical holes flaring away from the worm as shown in Fig. 4. The holes are advantageously conical and flare as shown, to reduce friction and lessen the power required to force the soap through the screen. It is supported at its periphery by rings l1 and is backed by heavy plate II which has a large number of relatively large holes which taper as shown. Behind this backing plate is set a four-bladed knife I. also directly fastened to worm II and rotating\with it, which serves to cut the filaments of soap into convenient lengths for feeding to the'plodder or extrusion device. This knife is fastened to the worm in a detachable manner so that it may be readily removed when it is desirable to remove the screen for cleaning.

Screen It is larger in diameter than cylinder II, as the cylinder diverges at the screen end, as This enlargement of the screen allowtheuseofscmewhatlcwerpressurcsinthe cylinder for forcing a given amount of soap the soap forward through nozzle 23. This nozzlev is constructed in the usual fashion and has guidebars 24 and annular conduit 25 through which hot water or steam may be circulated to heat the surface of the extruded bar of soap by heating the inner surface of the nozzle, preferably to about 110 to 118 F.

Both cylinder l2 and cylinder 22 are provided with fins 26 and jacket 21 so that cooling water may be circulated around the cylinders to main- I tain the temperature of the soap being forced through the cylinders by the worms-sufllciently low to insure the production of a bar of soap of proper consistency and plasticity in accordance with ordinary practice. maintained at about 80 F.

Worm H is directly keyed to shaft 28 and-is driven by it. This shaft rotates in bearings 29 which are constructed in the usual manner. Worm 2| is keyed to shaft 30 and is driven by it. This shaft rotates in a bearing made in the usual fashion except that it is provided with stuffin'g box 3|,packing 32, and gland 33 to prevent the ingress of air past shaft 3!) into vacuum chamber l6. Also the joints between bearing support 34a, cylinder 22 and stufiingbox 3| are provided with thin'rubber gaskets'to insure against the ingress of air at these points. The shafts are driven in any convenient manner.

Vacuum chamber I6 is formed by placing a metal hood 34 over opening 20 into the lower cylinder and over the screen I 4. Chamber I6 is made vacuum-tight by inserting rubber packing 35 between the metal hood and the parts of the cylinders with which it comes incontact. Opening 36 is provided either in the lower cylinder or in the metal hood for a connection to a suitable vacuum device (not shown).

The grinding head I 3 is shown in greater de tail in Figs. 2 and 3. This head consists of 32 knives which rotatewith the worm l l and which scrape against screen I l and prevent it from ing clogged up by ing head consists of a central portion 31, 8. Supporting ring at the periphery 3g, and knives 39. These knives scrape across the foraminous screen and are of such character that alternate knives force the soap against the screen because of inclined edges'as shown at 40, while the other knives are provided with right edges which scrape the surface ofthe screen accumulation of foreign particles which might clog up the screen. The grinding head also serves to protect the screen, inasmuch as it prevents large pieces of metal such as nails, wires, or bolts, from impinging against the screen anddamaging it. This grinding head is unnecessary for successful operation of the machine, but is advantageously used, as it considerably lengthens the period during which operation may be continued without cleaning the screen. For examis desirableto clean the The soap is preferably foreign matter. The grindclean and prevent the Y ing pie, using the grinding head, the machine may be operated for a week or more without cleaning, whereas without that grinding head, it may require daily cleaning.

Thus in carrying out my process, milled soap n flake or chip form is fed onto a rotating worm or screw and compacted and compressed and forced through a foraminous plate directly into an evacuated chamber in the form of filaments or strings of soap cut into convenient lengths. In the evacuated chamber, all air or permanent gas is removed from the soap which then passes to another screw or worm which again compresses and compacts the soap and forces it out through a nozzle in the form of a continuous bar'of soap which is free from striations or irregularities in texture and which is homogenews and plastic.

In the operation, all foreign matter which might be objectionable in the finished soap is removed by the foraminous plate. The consistency of the final soap and of the soap during the operation are controlled by providing cooling water around the cylinders in which the worms operate, in the usual manner. While it is not necessary to maintain any particular temperature of the soap mass during the operation, it is desirable to prevent an undue rise in the temperature of the soap which might adversely affect its texture or other properties, and hence is desirable to maintain the soap at or below about 80 F. l My process differs from other known processes for the production of toilet soap or partially dried milled soap, .in that it provides means for eliminating all striations or fissures in the soap by eliminating the air which or fissures before the soap is finally compacted and compressed into a bar. This process retains all of the advantages of the prior processes inasmuch as it provides for the elimination of hard particles or for their reduction in size to such (an f texture.

- of soap free from striations.

I claim:

1. The improvement in the manufacture of soap which comprises forcing milled soap through a foraminous plate into an evacuated chamber to remove air and other gases, and plodding the soap, while maintaining it under the vacuum, to produce soap free'from striations.

2. The process which comprises partially drysoap, milling such partially dried soap, forcing it through a screen, then subjecting it to a vacuum to remove air and other gases, and plodding the soapwhile maintaining it under the vacuum to produce soap free from striations.

causes .such striations Jonas ascnwama 

